A shotgun is also known as a scattergun, a coach gun and a riot gun. A shotgun is a firearm that typically designed to fire a shell holding numerous pellets called shot. The pellets fired from a shotgun spread upon leaving the barrel. Typically, the spread of shotgun used for hunting at 25 feet away, averages about 8 inches.
Shotguns come in a wide variety of barrel lengths, typically from 18 inches to 29 inches. The barrel length significantly affects the spread of the shot at the target, where shorter barrels deliver greater shot spread at any given distance with range. For civilian use, many countries establish a legal minimum barrel length that precludes easy concealment. In the United States, the minimum barrel length for civilian use is 18 inches (460 mm). Such laws are generally inapplicable to police and military authorities.
The military value of the shotgun was evidenced by its use during World War I by U.S. troops. Doughboys were issued 12-gauge pump action shotguns for use in close-quarters trench fighting to great effect. In jungle combat during World War II and Vietnam shotguns were common and effectively used when relatively close combat encounters could be expected. In urban combat situations, such as experienced in Iraq, shotguns were used to great effect to defeat the locks on doors when entering a building.
Shotguns are common weapons aboard naval vessels, which employ shotguns for shipboard security because the weapon is effective in repelling enemy boarding parties. Shotguns are also commonly used by military police units.
For both law enforcement and military engagements, the spread of pellets from a shotgun provides a tactical advantage in close quarters combat, such as within a building. The shotgun is widely used as a support weapon by police forces and specialized police and defensive shotguns are called riot shotguns.